The invention relates generally to the field of die stamping and more particularly to a method and apparatus for protecting a die and punch assembly from damage due to material jams.
Material stamping equipment, containing die and punch assemblies, stamps, forms or cuts patterns or holes in material that is fed into the die. As shown in FIG. 1, the stamping, forming or cutting is usually accomplished by a punch assembly 2 being driven into contact with the feed material 3 that is fed into the die 1. The feed material in turn is driven up against the die by the punch assembly. Material 4 that is stamped or cut out of the feed material 3 is ejected through holes 1a in the die if the stamping process does not become jammed. New feed material 3 is then advanced into the die 1 and material that has been stamped is advanced out of the die by the action of the press feed roll drive motor 5 and the press feed rolls 6.
It should be noted that the material stamping equipment, including the punch assembly 2, die 1, and material support 7, the press feed roll drive motor 5 and press feed rolls 6, and the in-position sensor 8 are all known in the art and are described and depicted in FIGS. 1, 2, 3, 4a, and 4b herein only as they relate to the current invention.
Unfortunately, as shown in FIG. 1 and FIG. 3, the material 4 stamped, formed or cut out from the pattern or hole in the feed material 3 does not always detach properly from the feed material and eject out of the die 1. This non-detaching material 4 either prevents the new feed material from fully advancing into the die 1 or remains in an unwanted position in the die causing damage to the die or renders subsequent work pieces improperly stamped.
Traditionally, as depicted in FIG. 2, and disclosed in U.S. Pat. No. 5,091,962, a die protection sensor 8, also known as an "in-position" sensor, is placed close to the feed material after said feed material has advanced through the die 1 to detect incorrectly positioned material. The problem with this traditional method is that, due to the high rate of speed at which material stamping machines operate, if a piece of material 4 is not properly stamped, formed or cut out of the feed material such that the material 4 is lodged in an undesirable position within the die as shown in FIG. 1 or FIG. 3, the punch assembly 2 will have already struck the jammed feed material and the die, potentially causing damage to the die, before the in-position sensor 8 can detect the incorrectly stamped material and stop the stamping machinery.
Buckle detectors have also been utilized to detect buckles 9 or other misfeeds in an effort to protect dies. However, the way such detectors have been traditionally used does not provide a satisfactory solution to the problem of material jamming because it provides only for stopping the press and still does not avoid damage to the material, die and punch assembly.
Accordingly, a method to protect dies from material jams, prior to the die stamping a subsequent work piece and thereby becoming damaged, has been desired.